stoneyridge: Enable IO CF9 in bootblock

If IO CF9 is not enabled, hard_reset() won't do anything in bootblock or
verstage.

BUG=b:110817463
TEST=built on grunt and made sure that hard_reset() reboots.

Change-Id: I5f091077a17db3dfe5b8e8367163312db6828360
Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Reviewed-on: https://review.coreboot.org/27267
Reviewed-by: Martin Roth <martinroth@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/stoneyridge/include/soc/southbridge.h

@@ -32,6 +32,8 @@
 #define  PSP_MAILBOX_BAR_EN		0x10
 
 /* Power management registers:  0xfed80300 or index/data at IO 0xcd6/cd7 */
+#define PM_DECODE_EN			0x00
+#define   CF9_IO_EN			BIT(1)
 #define PM_ISA_CONTROL			0x04
 #define   MMIO_EN			BIT(1)
 #define PM_PCI_CTRL			0x08

src/soc/amd/stoneyridge/southbridge.c

@@ -368,6 +368,13 @@ void sb_acpi_mmio_decode(void)
 	outb(byte, PM_DATA);
 }
 
+static void sb_enable_cf9_io(void)
+{
+	uint32_t reg = pm_read32(PM_DECODE_EN);
+
+	pm_write32(PM_DECODE_EN, reg | CF9_IO_EN);
+}
+
 void sb_clk_output_48Mhz(void)
 {
 	u32 ctrl;
@@ -542,6 +549,7 @@ void bootblock_fch_early_init(void)
 	sb_spibase();
 	sb_disable_4dw_burst(); /* Must be disabled on CZ(ST) */
 	sb_acpi_mmio_decode();
+	sb_enable_cf9_io();
 	enable_aoac_devices();
 }